Separation and determination of trace amounts of vanadium(V), chromium(III) and iron(III) with 2-(2-thienylazo)-5-diethylaminophenol chelates by high-performance liquid chromatography

Abstract

A reversed-phase high-performance liquid chromatographic method for the separation and the determination of vanadium(V), chromium(III) and iron(III) with 2-(2-thienylazo)-5-diethylaminophenol chelates on a C 18-bonded stationary phase by using methanol-tetrahydrofuran- (20:15:65, v/v/v) containing 0.05 M lithium sulphate and 0.04 M acetate buffer (pH 5.5) as mobile phase and with spectrophotometric detection at 570 nm was developed. The method has high sensitivity, the detection limits being 0.5 ppb for vanadium(V), 2 ppb for chromium(III) and 1 ppb for iron(III). Under the optimum conditions, most other metal ions did not interfere, e.g., up to 1000 μg of magnesium(III), cadmum(II), zinc(II), lead(II), manganese(II), calcium(II), barium(II), tin(II, IV) and tungsten (VI), 400 μg of thorium(IV), 200 μg of iron(II), bismuth(III), zirconium(IV), 150 μg of gallium(III) and 120 μg of lanthanum(III) in the determination of 2.5 μg of iron(III) and chromium(III) and 1 μg of vanadium(V). The method can be applied to the simultaneous determination of trace amounts of vanadium(V), chromium(III) and iron(III) in water, tea leaves and rice samples.